A radio controlled watch is known which receives a time code to correct time thereof. The time code has a predetermined format of successive frames of 60 seconds with each frame including 60 data pulses one occurring in an unit period of 1 second. The time code now in use in Japan includes a “P” signal that is high for 0.2 seconds from a start of a unit period, a “0” signal that is high for 0.5 seconds from a start of a unit period, and a “1” signal that is high for 0.8 seconds from a start of the unit period. Among these signals, the “P” signal is defined as a frame marker which indicates a start of each of the frames of the time code and serves also as a position marker which indicates each of divisions for data such as minutes, hours, days and years. Moreover, the “0” and “1” signals represent binary “0” and “1”, respectively, which can be applied to a time code format, thereby calculating a current exact time and date represented in minutes, hours, day, month, and year. A seconds synchronization point where, for example, a watch can be seconds-synchronized with the standard signal is represented by a rise of each data pulse. The time code, for example, AM-modulated, is carried by the standard signal, which is of 40 or 60 kHz, but a clear signal waveform indicative of the time code can not be received due to diffused reflections/attenuations in buildings and mixing of turbulent noise.
In the past, some propositions have been made which try to detect a seconds synchronization point in the time code accurately from the standard time and frequency signal even when the same contains noise. Japanese Patent Application TOKKAIHEI 2005-249632 discloses a technology that tries to detect a bit (or seconds) synchronization point by binarizing the detected signal at intervals of 0.1 seconds, listing groups of binarized data each for one second, and converting these groups of data to a step-like graph.
In the above-mentioned method, when the detected signal contains a little noise, the seconds synchronization point is detectable from a binarized version of the detected signal. However, if the detected signal contains a considerable noise such as would make it impossible to recover the original data pulses, the seconds synchronization point is not detectable.
An object of the present invention is to provide a time information receiver and radio controlled watch capable of detecting a seconds synchronization point with high accuracy from the detected signal even when the same contains a considerable noise.